Power staplers operated by pneumatic and/or electric actuators are widely used in document handling and document creation applications. Photocopiers and laser printers often incorporate a power stapler or "stitcher" in their mechanism to provide optional binding of completed documents.
FIG. 1 is an example of a typical implementation for a stitcher 10. A set of printed sheets 12 are fed either one at a time or as a group (as shown) to the stitcher 14.
The stitcher 14, itself, comprises an electromechanical and/or pneumatic stitcher shown schematically. A known stitcher such as the Hohner Universal 52/8 is contemplated. However, the principles of this invention are applicable to virtually any known stitcher mechanism. The stitcher 14 forms wire staples or "stitches" 16 as shown from a fed coil 18 of staple wire 20 in a conventional manner. The staple 16 is driven as shown by the arrows 22 by a reciprocating stitcher head 24 into a predetermined point on the stack of sheets 12 such as an upper corner as shown in FIG. 1.
Positioned opposite the stitcher head 24 is a clinching head 26 operated by pneumatic pressure in this example. The clincher head 26 bends the ends of the staple 16 inward upon themselves once the staple is forced completely through the stack. The resulting stapled stack is output to an output point 28 as shown in FIG. 1. As will be described further below, this invention has as an object the formation of improved staples by providing an improved clincher head. This invention also has as an object the stitching of variable thickness stacks of pages without requiring adjustment of the staple length.